U.S. patent number 4,356,102 [Application Number 06/199,589] was granted by the patent office on 1982-10-26 for dichroic liquid crystal compositions containing anthraquinone-based dyes.
This patent grant is currently assigned to General Electric Company. Invention is credited to Sigfried Aftergut, Herbert S. Cole, Jr..
United States Patent |
4,356,102 |
Aftergut , et al. |
October 26, 1982 |
Dichroic liquid crystal compositions containing anthraquinone-based
dyes
Abstract
Liquid crystal compositions having guest anthraquinone-based
dyes dissolved therein, are disclosed. The anthraquinone-based dyes
have the general formula: ##STR1## wherein at least one of X and X'
is a 5-membered ring connected to the lateral positions of the
lateral benzene rings in the anthraquinone molecule, the five
membered ring having the structure: ##STR2## wherein R is an alkoxy
alkyl radical, a straight chain or branched chain alkyl radical, a
phenyl radical, a benzyl radical and/or substituted derivatives of
the foregoing radicals. The anthraquinone-based dyes of the
invention may be used alone or with other compatible dyes as guest
dyes to form various colors for coloring the host liquid crystal
compositions. One preferred class of guest anthraquinone-based dyes
which are dissolved in the host liquid crystal material, are
various derivatives of
1,4-diamino-2,3-anthraquinone-dicarboximide.
Inventors: |
Aftergut; Sigfried
(Schenectady, NY), Cole, Jr.; Herbert S. (Scotia, NY) |
Assignee: |
General Electric Company
(Schenectady, NY)
|
Family
ID: |
22738181 |
Appl.
No.: |
06/199,589 |
Filed: |
October 22, 1980 |
Current U.S.
Class: |
252/299.1;
552/245; 552/256 |
Current CPC
Class: |
C09K
19/603 (20130101); C09B 5/2472 (20130101) |
Current International
Class: |
C09B
5/24 (20060101); C09B 5/00 (20060101); C09K
19/60 (20060101); C02F 001/13 (); C09K
003/34 () |
Field of
Search: |
;252/299.1 ;350/349
;260/326C |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2104 |
|
May 1979 |
|
EP |
|
2920730 |
|
Nov 1979 |
|
DE |
|
2902177 |
|
Jul 1980 |
|
DE |
|
55-127485 |
|
Oct 1980 |
|
JP |
|
2037803 |
|
Jul 1980 |
|
GB |
|
2045274 |
|
Oct 1980 |
|
GB |
|
Other References
Seki, H., et al.; Abstracts of the 8th International Liquid Crystal
Conference, Kyoto, Japan, L-1P (Jun. 30-Jul. 4, 1980). .
Uchida, T. et al.; Mol. Cryst. Liq. Cryst., vol. 63, pp. 19-44,
(1981). .
Aftergut, S. et al., Mol. Cryst. Liq. Cryst., vol. 78, pp. 271-277
(1981). .
Cox, R. J., Mol. Cryst. Liq. Cryst., vol. 55, pp. 1-32
(1979)..
|
Primary Examiner: Gron; Teddy S.
Attorney, Agent or Firm: Teoli; William A. Davis, Jr.; James
C.
Claims
What is claimed is:
1. A liquid crystal composition comprising:
a host liquid crystal material; and
at least one guest anthraquinone dye dissolved in said host liquid
crystal material, said anthraquinone dye having the general
formula: ##STR30## wherein R is selected from the group consisting
of: a cyclohexyl radical;
a phenyl radical;
a benzyl radical;
a substituted phenyl radical having the formula: ##STR31## a
substituted benzyl radical having the formula: ##STR32## where R"
is in the para-position and is selected from the group consisting
of halogen, cyano, nitro, alkoxy, hydroxyl, amino, alkylamino,
dialkylamino, alkyl wherein the alkyl is from about 1 to about 10
carbon atoms, arylamino and esters having the formula: ##STR33##
wherein R' is selected from the group consisting of alkyl,
substituted alkyl, aryl and substituted aryl; R"' is hydrogen or
alkyl having from about 1 to about 3 carbon atoms; and n is an
integer from 0 to 5.
2. The liquid crystal composition of claim 1, wherein the
anthraquinone dye is 1,4-diamino-N-phenyl-2,3-anthraquinone
dicarboximide.
3. The liquid crystal composition of claim 1, wherein the
anthraquinone dye is
1,4-diamino-N-(1-methylbenzyl)-2,3-anthraquinone dicarboximide.
4. The liquid crystal composition of claim 1, wherein the
anthraquinone dye is 1,4-diamino-N-cyclohexyl-2,3-anthraquinone
dicarboximide.
5. The liquid crystal composition of claim 1, wherein the
anthraquinone dye is
1,4-diamino-N-p-hydroxyphenyl-2,3-anthraquinone dicarboximide.
6. The liquid crystal composition of claim 1, wherein the
anthraquinone dye is 1,4-diamino-N-phenylbenzoate-2,3-anthraquinone
dicarboximide.
7. The liquid crystal composition of claim 1, wherein the
anthraquinone dye is
1,4-diamino-N-(p-hexoxyphenyl)-2,3-anthraquinone dicarboximide.
Description
This invention relates to liquid crystal compositions, and more
particularly, to dichroic liquid crystal compositions containing
anthraquinone-based dyes.
Liquid crystals are conventionally used in conjunction with one or
more dyes to obtain improved colors when liquid crystals are used
in liquid crystal displays. In such cases, a host liquid crystal
composition comprises a host liquid crystal material and guest dye
dissolved in the host liquid crystal material. The guest dyes which
may be used alone or in combination with other dyes to achieve a
desired color, preferably have certain properties which enhance
their use in liquid crystal compositions. These properties include
dichroism, solubility of the dye in the liquid crystal and high
order parameter.
Dichroism is the property whereby an oriented assembly of dye
molecules exhibit relatively low absorption of a given wavelength
in one state of orientation and a relatively high absorption of the
same wavelength in another state of orientation with respect to the
light source. The orientation can be brought about by dissolution
of the dye in a liquid crystal solvent.
Solubility must be sufficiently high so that thin layers, for
example, of ten micrometers, have adequate light absorption in one
of the oriented states. In certain instances, the solubility of a
particular dye may be relatively low, however, the dye may still be
used in conjunction with other dyes which are also soluble in the
liquid crystal host so that there is adequate light absorption in
one of the oriented states.
Order parameter is a quantative measure of the degree of molecular
order or alignment in a given system. High order parameter is
promoted by dyes with elongated shape having a large ratio of
molecular length to breadth, similar to the shape of the molecules
of a liquid crystal host material. To insure an elongated shape,
the molecules should have a rigid structure. The brightness and
contrast are both related to the order parameter, normally
designated as S, of the dye, where S=(R-1)/(R+2), and R is the
ratio of light absorption in the dye measured with a polarizer
respectively parallel and perpendicular to the nematic director of
the liquid crystal host at the wavelength of maximum absorption.
Advantageously, the order parameter should be at least 0.60, and
preferably, as high as possible, to achieve a minimum desired
contrast ratio while still allowing a liquid crystal guest-host
display to be fabricated with a reasonable brightness
parameter.
The eye is sensitive to radiation in the 400-700 nm wavelength
range, however, there are few dyes which absorb radiation above
about 650 nm which are also compatible with liquid crystal
materials and which have a sufficient order parameter, S.
To fabricate a dichroic liquid crystal display with a neutral black
color, for example, the radiation present in a source of
illumination, such as, daylight, incandescent lamps or fluorescent
lamps, to which the eye is sensitive, must be absorbed to a
substantial degree at all wavelengths from 400-700 nm. To make a
good blue-colored or green-colored dichroic liquid crystal display,
radiation in the 600-700 nm range must also be substantially
absorbed to prevent a reddish hue since radiation in the 600-700 nm
range is perceived as red. If the absorption of a dichroic liquid
crystal in the 600-700 nm range is insufficient, black and blue
displays have a reddish hue, and green displays do not have a
pleasing green appearance. In order to overcome this problem it is
necessary to provide blue dyes having an absorption peak at
wavelengths greater than about 650 nm, with a sufficient order
parameter, for example, above about 0.60, and with sufficient
solubility in liquid crystal compositions.
Blue dichroic dyes of the azo and anthraquinone types are well
known in the prior art. Blue azo dyes of high order parameter and
absorption peak at 595-610 nm are commercially available. These
dyes also absorb at wavelengths greater than 610 nm, but the
absorption at the higher wavelengths is relatively low. One
anthraquinone dye, commercially available under the trade name
Waxoline Green G, has an absorption peak of about 650 nm, however,
this dye has a low order parameter of only about 0.4 to 0.45 and is
therefore not satisfactory for making liquid crystal displays of
good black, blue or green colors.
Other commercially available anthraquinone dyes, such as dye D-27
sold by B.D.H. Chemicals, have better order parameter, for example,
0.60 to 0.66, however, the peak absorption of such dyes is less
than that of the Waxoline Green G described above, the peak
absorption dye of D-27 being about 612 nm. Another anthraquinone
dye, 4,8-diamino-1,5-dihydroxy-3-(4-heptyloxyphenyl) anthraquinone,
produced by Hoffman-LaRoche Company, has an order parameter of 0.74
with peak absorption at 645 nm. This is an improvement over
previous anthraquinone-based dyes, however, it does not effectively
absorb light beyond 650 nm to produce the desirable features and
effects expressed above.
A blue anthraquinone-based dye known as 1,4-di-n-butylamino
anthraquinone is used in conjunction with other dyes in U.S. Pat.
No. 3,864,022 and U.S. Pat. No. 3,960,750. This dye is used in
conjunction with liquid crystal molecules, however, it has a peak
absorption of less than 650 nm and a relatively low order
parameter. Other photostable anthraquinone pleochroic dyes have
been disclosed by B.D.H. Chemicals Limited, Poole, Dorset, however,
such dyes have absorption peaks less than 650 nm and generally have
relatively low order parameters, that is, S=<0.60.
Blue dyes of the anthraquinone series suitable for the coloring of
polyethylene terephthalate fibers known as "Dacron", are described
in U.S. Pat. No. 2,628,963. The dyes in U.S. Pat. No. 2,628,963 are
the 1,4-diamino-2,3-anthraquinone-dicarboxamides. These dyes are
used in the dyeing of such fibers as "Dacron" in blue shades, and
they result in colored fibers having excellent light-fastness and
gas-fume fastness. There is no disclosure in U.S. Pat. No.
2,628,963 relative to the use of the anthraquinone series of dyes
disclosed therein in liquid crystal compositions.
Accordingly, it is the primary object of this invention to provide
liquid crystal compositions which overcome the disadvantages
discussed above.
It is another object of this invention to provide a liquid crystal
composition containing blue dye with an absorption peak at
wavelengths greater than 650 nm and with an order parameter greater
than 0.60.
Another object of this invention is to provide an improved dichroic
liquid crystal formulation containing anthraquinone-based dyes with
absorption peaks at wavelengths greater than 650 nm.
Still another object of this invention is to provide a dichroic
liquid crystal composition containing a plurality of dyes including
at least one anthraquinone-based dye having a maximum absorption
peak at a wavelength greater than 650 nm and an order parameter
greater than 0.60.
These and other objects are accomplished by dissolving
anthraquinone-based dyes having absorption at wavelengths greater
than 650 nm and an order parameter greater than 0.60 in a liquid
crystal host material. A guest anthraquinone-based dye having a
five-membered, N-substituted dicarboximide ring structure joined to
the two lateral carbon atoms of at least one lateral benzene ring
of the anthraquinone molecule is dissolved in a host liquid crystal
material to color the liquid crystal material. The carbon atoms of
the two carbonyl groups of the dicarboximide are bonded
respectively to the two lateral carbon atoms of the lateral benzene
ring to form the five-membered ring.
In accordance with the present invention, there is provided a
liquid crystal composition comprising a host liquid crystal
material and a guest anthraquinone dye dissolved in said host
liquid crystal material, the anthraquinone dye having the general
formula: ##STR3## wherein at least one of X and X' is a
five-membered ring connected to the two lateral positions of the
lateral benzene rings in the anthraquinone molecule, the
five-membered ring having the structure: ##STR4## wherein R is
selected from the group consisting of alkoxyalkyl radical, straight
chain or branched chain alkyl radical having from one to about ten
carbon atoms and halogen, amino and nitro derivatives thereof,
phenyl radical, substituted phenyl radical, benzyl radical and
substituted benzyl radical, wherein the substituted phenyl and
substituted benzyl radicals are substituted with halogen, cyano,
nitro, alkoxy, hydroxyl, amino, alkylamino, dialkylamino, alkyl
radical wherein the alkyl is from one to about ten carbon atoms,
arylamino and ester having the formula: ##STR5## wherein R' is
selected from the group consisting of alkyl radical, substituted
alkyl radical, aryl and substituted aryl; and wherein Y, Y', Z and
Z' are one of the following substituents: hydrogen, amino,
alkylamino, dialkylamino, nitro, alkyl radical having from about
one to ten carbon atoms, substituted alkyl radical having from
about one to about ten carbon atoms, halogen, cyano and
hydroxy.
By dissolving at least one guest anthraquinone dye in a host liquid
crystal material, the guest anthraquinone dye having the general
formula: ##STR6## wherein X, X', Y, Y', Z and Z' are defined above,
in at least one host liquid crystal material, improved liquid
crystal compositions having improved color because of the maximum
absorption peak or maximum absorption peaks greater than 650 nm and
the high order parameter of the guest anthraquinone-based dye or
dyes are obtained. In accordance with the present invention,
improved black liquid crystal displays and improved blue liquid
crystal displays have been prepared without a reddish hue, and
green liquid crystal displays have been prepared with a more
pleasing green appearance. In accordance with the present
invention, dichroic liquid crystal compositions containing dyes
with an absorption peak at a wavelength greater than 650 nm and
with an order parameter of at least 0.60 have been prepared and
produce improved colors in liquid crystal displays.
Although there is no intention of being limited to any particular
theory, it appears that the elongation of the dye molecule in a
symmetrical fashion along the major axis of the anthraquinone
nucleus results in the improved performance of the dyes of the
invention in liquid crystal materials. The major axis is the axis
or line which divides and passes through the three consecutive
benzene rings of the anthraquinone molecule and continues through
the N-R in the dicarboximide group attached to the lateral benzene
ring. Thus, the anthraquinone dye molecule is elongated by the
5-membered ring attached to the two lateral carbon atoms of one or
both of the lateral benzene rings. The dye is further elongated by
substituting various groups upon the nitrogen atom of the
dicarboximide ring structure.
The basic dye molecule showing numbered substitution atoms of the
anthraquinone-based dyes of the present invention is shown below
wherein a dicarboximide is attached to the two lateral carbon atoms
of one of the lateral benzene rings of the anthraquinone-based dye
structure. ##STR7## The anthraquinone-based dye structure is
represented by the three adjacent benzene rings in the above
molecular configuration. The dicarboximide is joined to one of the
lateral benzene rings at the outermost (the two lateral) carbon
atoms designated as carbon atom number 2 and carbon atom number 3.
Thus, the one side of the five-membered ring of the five-membered,
N-substituted ring structure is actually formed by the bonding of
or joining of the carboxyl groups of the dicarboximide with the two
lateral carbon atoms of the lateral benzene ring of the
anthraquinone molecule, and as used herein, this is defined as a
five-membered, N-substituted dicarboximide ring structure joined to
the two outermost or lateral carbon atoms of the lateral benzene
ring of the anthraquinone dye. In accordance with the present
invention, a dicarboximide group may also be attached to the
anthraquinone molecule at the other lateral benzene ring at the
outermost (the two lateral) carbon atoms designated as carbon atom
number 6 and carbon atom number 7. In accordance with the present
invention, there may be two dicarboximide ring structures upon the
anthraquinone dye molecule, or there may be only one dicarboximide
ring structure at either one of the lateral benzene rings of the
anthraquinone-based dye. As used herein, one lateral benzene ring
is the benzene ring embracing carbon atoms 1-4, and the other
lateral benzene ring is the benzene ring embracing carbon atoms
5-8. There must be at least one dicarboximide group upon the
anthraquinone-based dye structure, either at carbon atoms 2 and 3
or at carbon atoms 6 and 7. Any of the numbered carbon atoms in the
dye structure shown above may be substituted with various groups
and/or radicals as long as there is at least one dicarboximide
structure at carbon atoms 2 and 3 or carbon atoms 6 and 7. The
major axis referred to above is that line which is drawn through
the three adjacent benzene rings in the anthraquinone-based dye
structure and which passes through the nitrogen and the "R"
substituted upon the nitrogen in the dicarboximide group or groups
attached to the lateral benzene rings of the dye molecule. Thus,
the major axis passes through the lateral benzene rings between
carbon atoms 2 and 3 and between carbon atoms 6 and 7. Various
groups which may be substituted in the numbered positions of the
molecular structure set forth above and various derivatives thereof
are described in more detail below.
These and various other objects, features and advantages of the
invention can be best understood from the following detailed
description.
The anthraquinone-based dyes of the present invention have the
general formula: ##STR8## wherein at least one X and X' is a
five-membered ring connected to the lateral benzene ring at the two
outermost or lateral carbon atoms upon the lateral benzene rings
and designated in the molecular structure as carbon atoms 2 and 3
and carbon atoms 6 and 7. The five-membered ring of the present
invention is an N-substituted dicarboximide wherein each of the two
carbonyl groups thereof joins or connects the lateral benzene ring
at the two outermost or lateral carbon atoms of the lateral benzene
rings. The N-substituted five-membered ring of the present
invention has the following structure: ##STR9## wherein R may be
any of various groups or radicals set forth below. As discussed
above, either X or X' or both X and X' can be the five-membered
dicarboximide ring structure connected to the lateral benzene rings
of the anthraquinone-based dye structure. However, in accordance
with the present invention, where only one of X or X' is a
5-membered dicarboximide ring attached to a lateral benzene ring of
the anthraquinone-based dye, the lateral or outermost carbon atoms
of the other lateral benzene ring, that is, carbon atoms 2 and 3 or
carbon atoms 6 and 7 of the anthraquinone-based dye structure, may
be substituted with hydrogen atoms, or the two positions may be
substituted by any of the groups described herein for Y, Y', Z and
Z'. Thus, if X represents a 5-membered dicarboximide ring, as in
the formula set forth above, X' may also be a 5-membered
dicarboximide ring substituted upon the outermost or lateral carbon
atoms of the lateral benzene ring, or X' may represent hydrogen
atoms substituted upon the lateral or outermost carbon atoms of the
lateral benzene ring, or X' may also represent amino groups,
alkylamino groups, dialkylamino groups, nitro groups, alkyl
radicals having from about 1 to about 4 carbon atoms, substituted
alkyl radicals having from about 1 to about 4 carbon atoms, halogen
groups, cyano groups, hydroxy groups and combinations thereof
substituted upon the lateral carbon atoms of the lateral benzene
ring, or if X' is a 5-membered dicarboximide ring upon the lateral
benzene ring of the anthraquinone-based dye structure, X may be
hydrogen atoms, amino groups, alkylamino groups, dialkylamino
groups, nitro groups, alkyl radicals having from about 1 to about 4
carbon atoms, substituted alkyl radicals having from about 1 to
about 4 carbon atoms, halogen groups, cyano groups, hydroxy groups
and combinations thereof substituted upon the two lateral or
outermost carbon atoms of the lateral benzene ring.
In the above general formula, Y, Y', Z and Z' may be any one of the
following substituents including hydrogen, amino groups, alkylamino
groups, dialkylamino groups, nitro groups, alkyl radicals having
from about 1 to about 4 carbon atoms, substituted alkyl radicals
having from about 1 to about 4 carbon atoms, halogen groups, cyano
groups and hydroxy groups, and they may be substituted at the
positions of the benzene ring shown as carbon atoms 1,4,5 and 8 in
the anthraquinone-based dye molecular structure set forth above.
Any of the replaceable hydrogen atoms on the lateral benzene rings
of the anthraquinone dye, wherein at least one of the lateral
benzene rings has an N-substituted dicarboximide joined to the two
outermost carbon atoms to form a 5-membered ring, may be
substituted with various substituents normally used in dyes
including chromophoric groups, various functional groups and
various non-functional groups. Examples of such groups include the
atoms, radicals and other groups specified for Y, Y', Z and Z'.
As used herein, and unless otherwise defined, halogen is chlorine,
bromine, iodine and fluorine; alkyl is straight chain or branched
chain and has from about 1 to about 10 carbon atoms; the alkyl
group of alkylamino (monoalkylamino) and dialkylamino has from
about 1 to about 4 carbon atoms and may be straight chain or
branched chain; aryl is benzene, naphthalene, or anthracene;
substituted aryl is any of the foregoing substituted with halogen,
nitro, amino, alkyl, cyano and/or hydroxy; arylamino is any of the
foregoing amino-substituted aryl compounds; and the alkyl and
alkoxy of the alkoxyalkyl are each from about 1 to about 4 carbon
atoms.
Examples of various atoms, radicals and groups which may be
substituted upon the carbon atoms of the lateral benzene rings as
discussed above, include hydrogen; amino (--NH.sub.2) groups;
monoalkylamino (--NHR) wherein R is an alkyl group having from
about 1 to about 4 carbon atoms and includes, for example,
monoisopropylamino, monobutylamino, monoisobutylamino,
mono-n-propylamino, monoethylamino, monomethylamino, and the like;
dialkylamino (--NR.sub.2) wherein R is an alkyl group having from
about 1 to about 4 carbon atoms and includes, for example,
dimethylamino, diethylamino, di-n-propyl-amino, methylethylamino,
ethylbutylamino, di-n-butylamino, and the like; nitro (--NO.sub.2);
alkyl having from about 1 to about 4 carbon atoms and including
methyl, ethyl, n-propyl, isopropyl, n-butyl and isobutyl;
substituted alkyl radicals having from about 1 to about 4 carbon
atoms and embracing the species described above and their halogen,
nitro, cyano and hydroxy derivatives, such as, for example,
chloromethyl, bromoethyl, chlorobutyl, fluoropropyl, bromopropyl,
nitromethyl, nitroethyl, nitrobutyl, cyanomethyl, cyanopropyl,
cyanoisopropyl, hydroxymethyl, hydroxypropyl, 1-hydroxybutyl,
2-hydroxybutyl, and the like; halogen, such as chlorine, fluorine,
iodine and bromine; cyano (CN); and hydroxy (--OH).
Examples of the N-substituted groups upon the 5-membered
dicarboximide structure shown below: ##STR10## include those
species wherein R is an alkoxyalkyl radical, such as, methoxymethyl
(--CH.sub.2 OCH.sub.3), methoxyethyl (--CH.sub.2 CH.sub.2
OCH.sub.3), 3-methoxy-propyl (--CH.sub.2 CH.sub.2 CH.sub.2
OCH.sub.3), 4-methoxybutyl (--CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2
OCH.sub.3), 3-ethoxypropyl (--CH.sub.2 CH.sub.2 CH.sub.2 OCH.sub.2
CH.sub.3), 2-ethoxypropyl (--CH.sub.2 --CH.sub.2 (OCH.sub.2
CH.sub.3)--CH.sub.3), and the like. R substituted upon the nitrogen
atom of the dicarboximide ring structure may also be a straight
chain or branched chain alkyl radical having from about one to
about ten carbon atoms and includes, for example, methyl, ethyl,
propyl, n-butyl, pentyl, hexyl, decyl and the like, and the
branched chain alkyl radicals, such as isopropyl, isobutyl,
isoamyl, isoheptyl, isononyl and the like. The straight chain alkyl
radicals and the branched chain alkyl radicals may also be
substituted with halogen atoms such as chlorine, bromine, iodine
and fluorine, for example, 3,3-dichloropropyl, 4-bromobutyl,
trichloromethyl, 2,2-difluoroethyl, and the like; or they may be
substituted with any conventional group which normally replaces
hydrogen including nitro, cyano, amino, hydroxy, and the like. R
substituted upon the nitrogen of the dicarboximide ring structure
may also embrace phenyl radicals and substituted phenyl radicals
having the formula: ##STR11## benzyl radicals, and substituted
benzyl radicals, and substituted benzyl radicals having the
formula: ##STR12## where R" is in the para-position and may be any
of several groups including hydrogen, halogen, such as chlorine and
bromine; cyano; nitro, hydroxy, alkyl, substituted alkyl, and the
like. R" may also be straight chain alkyl radical having from about
1 to about 10 carbon atoms; branched chain alkyl radical having
from about 1 to about 10 carbon atoms; substituted straight chain
or branched alkyl radical having from about 1 to about 10 carbon
atoms; amino; alkoxy; alkylamino; dialkylamino; hydroxy; phenol;
arylamino; and esters having the formula: ##STR13## wherein R' may
be alkyl, substituted alkyl, aryl and substituted aryl, the
substituted alkyl and substituted aryl being substituted with
hydroxy, alkyl, alkoxy, amino, monoalkylamino, dialkylamino, cyano,
phenyl, and the like. R"' can be hydrogen or alkyl having from
about 1 to about 3 carbon atoms, and n is an integer from 0 to 5.
The alkoxy groups discussed above for R' and R" generally include
such species as methoxy, ethoxy, propoxy, butoxy, isobutoxy, and
alkoxy groups having up to about 10 carbon atoms. The
monoalkylamino radicals for R' and R" include, for example,
monoethylamino, monomethylamino, monopropylamino, monobutylamino,
monoisobutylamino, and the like; and the dialkylamino radicals for
R' and R" include, for example, dimethylamino, diethylamino,
methylethylamino, ethylbutylamino, dibutylamino, and the like. The
alkyl of the mono- and di- alkylamino groups may be from about 1 to
about 10 carbon atoms. The esters discussed above include, for
example, methylbenzoate, ethylbenzoate, propylbenzoate,
butylbenzoate, octylbenzoate, phenylbenzoate,
p-hydroxyphenylbenzoate, ethoxyphenylbenzoate,
3,5-diaminophenylbenzoate, 3,5-dimethylphenylbenzoate,
p-ethylphenylbenzoate, monoethylaminophenylbenzoate,
dibutylaminophenylbenzoate, cyanophenylzoate, biphenylbenzoate, and
the like. The straight chain or branched chain substituted or
unsubstituted, groups for R', R" and R"' are the same as those
previously defined for other substituents, such as Y, Y', Z and Z'
defined above.
One preferred class of liquid crystal compositions of the present
invention comprises a host liquid crystal material; and at least
one guest anthraquinone dye dissolved in the host liquid crystal
material, the anthraquinone dye having the general formula:
##STR14## wherein R is the same as defined above and includes: (a)
alkoxyalkyl radical; (b) straight chain alkyl radical having from
about 1 to about 10 carbon atoms and substituted derivatives, such
as, nitro, halogen, amino, cyano and the like, thereof; (c)
branched chain alkyl radicals having from about 1 to about 10
carbon atoms and substituted derivatives, such as, nitro, halogen,
amino, cyano and the like, thereof; (d) phenyl radicals; (e) benzyl
radicals; (f) substituted phenyl radicals; and (g) substituted
benzyl radicals, both the phenyl radicals and the benzyl radicals
being substituted in the para-position with, for example, halogen
groups, cyano groups, nitro groups, amino groups, alkoxy groups,
hydroxyl, monoalkylamino groups, dialkylamino groups, straight
chain or branched alkyl radicals (substituted or unsubstituted),
wherein the alkyl is from about 1 to about 10 carbon atoms,
arylamino groups and alkyl esters, substituted alkyl esters, aryl
esters, and substituted aryl esters.
Examples of preferred anthraquinone dyes having the preferred
general formula as set forth above include, for example,
1,4-diamino-N-(3-methoxypropyl)-2,3-anthraquinone dicarboximide;
1,4-diamino-N-(4-butoxypropyl)-2,3-anthraquinone dicarboximide;
1,4-diamino-N-(3-methoxyethyl)-2,3-anthraquinone dicarboximide;
1,4-diamino-N-(3-ethoxypropyl)-2,3-anthraquinone dicarboximide;
1,4-diamino-N-(isopropyl)-2,3-anthraquinone dicarboximide;
1,4-diamino-N-ethyl-2,3-anthraquinone dicarboximide;
1,4-diamino-N-butyl-2,3-anthraquinone dicarboximide;
1,4-diamino-N-octyl-2,3-anthraquinone dicarboximide;
1,4-diamino-N-phenyl-2,3-anthraquinone dicarboximide;
1,4-diamino-N-chlorophenyl-2,3-anthraquinone dicarboximide;
1,4-diamino-N-ethylbenzoate-2,3anthraquinone dicarboximide;
1,4-diamino-N-nitrophenylbenzoate-2,3-anthraquinone dicarboximide;
1,4-diamino-N-(1-methylbenzyl)-2,3-anthraquinone dicarboximide; and
1,4-diamino-N-(1-methylchlorobenzyl)-2,3-anthraquinone
dicarboximide; and 1,4-diamino-N-butylphenyl-2,3-anthraquinone
dicarboximide.
The 1,4-amino-2,3-anthraquinone dicarboximides are illustrated and
disclosed in U.S. Pat. No. 2,628,963, and two preferred methods of
making the 1,4-diamino-2,3-anthraquinone dicarboximides are
disclosed therein. The 1,4-diamino-2,3-anthraquinone dicarboximides
of U.S. Pat. No. 2,628,963 wherein the nitrogen atom of the
dicarboximide ring structure is substituted with a substituent
other than hydrogen, and preferably substitutents as disclosed,
discussed and defined above, may be used as guest
anthraquinone-based dyes in a host liquid crystal material in
accordance with the present invention. U.S. Pat. No. 2,628,963 is
incorporated herein by reference for its disclosure in preparing
the guest anthraquinone-based dyes used in the host liquid crystal
materials of the present invention. As disclosed therein, the
N-substituted 1,4-diamino-2,3-anthraquinone dicarboximides are
prepared by different methods, for example an appropriate
1,4-diamino-2,3-anthraquinone dicarboxamide is heated in
concentrated sulfuric acid at temperatures of 75.degree. to
85.degree. C.; then after cooling to a lower temperature, water is
slowly added, and as the solution is cooled, crystals separate out
which are filtered off. These crystals may be washed in hot water,
which converts them from orange to a blue color. The
1,4-diamino-2,3-anthraquinone dicarboximides may also be prepared
from the 1,4-diamino-2,3-anthraquinone dicarbonitriles by heating
in concentrated sulfuric acid with the addition of a secondary
alcohol, or when the straight 1,4-diamino-2,3-anthraquinone
dicarboximide is to be produced, the alcohol is omitted. The
1,4,5,8-tetramino-2,3,6,7-anthraquinone tetracarboximides can be
made by substantially the same process described above and in U.S.
Pat. No. 2,628,963 using, for example, the appropriate
1,4,5,8-tetramino-2,3,6,7-anthraquinone tetracarboxamide. More
specific reaction conditions and details are disclosed in U.S. Pat.
No. 2,628,963.
The N-alkyl substituted 1,4-diamino-2,3-anthraquinone
dicarboximides are prepared from the 1,4-diamino-2,3-anthraquinone
dicarboximide prepared by either of the methods discussed above my
mixing the 1,4-diamino-2,3-anthraquinone dicarboximide with an
alkylamine solution in methanol, for example, when the N-methyl
substituted compound is desired, methylamine solution in methanol
is used. When the n-butyl substituted compound is required,
n-butylamine solution in methanol is used. The reaction mixture is
used in the presence of ortho-dichlorobenzene and methanol and is
heated with stirring in an autoclave for about 4 hours at from
175.degree. C. to 180.degree. C. After cooling, the crystals which
form are separated and washed with alcohol until the filtrate is
almost colorless.
When branched-chain anthraquinones are desired, for example,
1,4-diamino-N-isobutyl-2,3-anthraquinone dicarboximide, the
equivalent branched chain alkylamine, isobutylamine, is used in the
foregoing process. Likewise, benzylamine is used in the foregoing
reacton and process when 1,4-diamino-N-benzyl-2,3-anthraquinone
dicarboximide is desired. N-alkoxyalkyl substituted anthraquinone
dicarboximides are obtained by using the desired alkoxyalkylamine,
for example, methoxypropylamine, ethoxyethylamine, and the like in
the foregoing process. When the corresponding N-substituted phenyl
radical is desired in the nitrogen-substituted dicarboximide, the
corresponding aniline is used, for example, aniline,
dichloroaniline, para-cyanoaniline, para-nitro-aniline,
para-hydroxyaniline, para-propoxyaniline, para-phenylenediamine,
paraethylamino aniline, 3,5-dimethylamino aniline, p-toluidine,
para-ethyl aniline, 3,5-dipropyl aniline and the like.
In other embodiments, the esters of
1,4-diamino-N-phenyl-2,3-anthraquinone dicarboximide and the
1,4-diamino-N-benzyl-2,3-anthraquinone dicarboximide are prepared
by reacting the appropriate chloride with
1,4-diamino-N-phenyl-2,3-anthraquinone dicarboximide and
1,4-diamino-N-hydroxybenzyl-2,3-anthraquinone dicarboximide
respectively, to form the corresponding ester. For example,
1,4-diamino-N-phenyl-2,3-anthraquinone dicarboximide is reacted
with hexyloxybenzoyl chloride to form the correponding ester,
1,4-diamino-N-phenylhexyloxybenzoate-2,3-anthraquinone
dicarboximide. Various other alkyl esters, substituted alkyl
esters, aryl esters and substituted aryl esters may be substituted
upon the nitrogen-substituted phenyl radical and the N-benzyl
substituted radical, for example, methylbenzoate, ethylbenzoate,
and other esters of the substituted phenyl radical having the
formula: ##STR15## and the substituted benzyl radical having the
formula: ##STR16## where R" is in the para-position and is an ester
having the formula: ##STR17## wherein R' is selected from the group
consisting of alkyl, substituted alkyl, aryl and substituted aryl,
and R"' is hydrogen or alkyl having from about 1 to about 3 carbon
atoms, and n is integer from about 0 to about 5.
Other 1,4-diamino-N-substituted-2,3-anthraquinone dicarboximides
and the method of making said dicarboximides are disclosed in U.S.
Pat. No. 2,628,963, and one skilled in the art can easily
substitute any conventional compound upon the nitrogen atom of the
dicarboximide ring structure upon the lateral benzenes of the
anthraquinone molecule of the 1,4-diamino anthraquinone compound or
any of the other equivalent compounds of the present invention. The
method of preparing the N-substituted anthraquinone dicarboximides
is not critical in the practice of the present invention, and one
skilled in the art can easily adapt common reaction processes and
mechanisms for substituting various positions upon the
anthraquinone molecular structure and upon the nitrogen atoms in
the dicarboximide upon the lateral benzene ring or lateral benzene
rings of the anthraquinone dye molecule.
It is also within the purview of one skilled in the art to
substitute various functional groups, non-functional groups, and
chromophoric groups for hydrogen atoms upon the basic molecular
structure of anthraquinone, that is, various functional groups,
non-functional groups and/or chromophoric groups may be substituted
for X, X', Y, Y', Z and/or Z' when at least one X or X' is a
5-membered ring connected to the benzene ring at the two outermost
or lateral carbon atom positions (numbered positions 2 and 3 and/or
6 and 7 of the lateral benzene rings of the anthraquinone
molecule), the five-membered ring having the basic dicarboximide
structure and the carbonyl groups of the dicarboximide being bonded
to the two adjacent lateral positions upon the lateral benzene ring
of the anthraquinone molecule. Conventional reactions, reaction
mechanisms, processes and reagents known to those skilled in the
art, can be used to incorporate such groups upon the anthraquinone
molecule at the designated positions, namely, carbon atoms 1-8 as
numberer in the general formula.
The anthraquinone-based dyes having the 5-membered,
nitrogen-substituted dicarboxmide ring structure can be used in any
conventional manner. However, in certain cases they are not used
along in liquid crystal compositions and may be used as a plurality
of dyes and/or in combination with other dyes, modifiers or
adjuvants. Because certain of the dyes have relatively low
solubility in the liquid crystals, the dyes are not used by
themselves in liquid crystal displays, however, the dyes are useful
as additives n conjunction with other dyes to improve the color of,
for example, black, green and blue displays. Accordingly, the
anthraquinone-based dyes of this invention are used with liquid
crystal host materials well-known in the art to improve the color
of the liquid crystal composition for use in a liquid crystal
display. When the anthraquinone-based dyes of this invention are
used with a crystal host, they are called guest dyes and they are
dissolved in the host liquid crystal material, that is, the guest
anthraquinone-based dye is soluble in the host liquid crystal
material. Many of the anthraquinone-based dyes used in accordance
with the present invention require mild heat, for example, above
ambient to about 110.degree. C. to promote their dissolution in the
host liquid crystal.
In accordance with the present invention, it is not critical how
much of the dye is present in the host liquid crystal as long as
the dye is soluble therein. In preferred embodiments, about 0.05%
by weight to about 1.0% by weight, and more preferably about 0.1%
by weight to 0.5% by weight, based upon the weight of the liquid
crystal host material, of the dye of this invention or mixtures of
dyes of this invention are present in the host liquid crystal. One
skilled in the art can adjust the amount of anthraquinone-based dye
having at least one 5-membered, N-substituted dicarboximide
structure upon the anthraquinone molecule as desired and can
determine the maximum solubility of the dye and/or the amount
required for maximum absorption at the wavelengths above 650 nm.
The upper limit of the amount of dye varies with the solubility of
the particular dye in the host liquid crystal. The amount of guest
dichroic anthraquinone-based dye of the present invention in the
host liquid crystal material is that amount up to the limit of
maximum solubility in the host of the anthraquinone-based dye
required to color, tint or shade the host liquid crystal, required
to add to the blue color of the host liquid crystal material, or
required to contribute to the color of a mixture of dyes used in
the host liquid crystal material, e.g., the use of the blue
anthraquinone-based dye or dyes of this invention with dyes of
other colors to improve the black, blue, green or other color of
guest dyes in the host liquid crystal.
The guest anthraquinone-based dichroic dyes of this invention are
particularly useful in black liquid crystal displays because
improved black liquid crystal materials can be obtained by mixing
dichroic dyes of various colors in proper proportions to obtain a
material which absorbs radiation in the spectral range of about
400-700 nm, and the anthraquinone-based dyes of this invention
substantially improve the absorption in the 650-700 nm region (the
red region) of such dye mixtures. Thus, in accordance with the
present invention, improved black, green and blue dichroic liquid
crystal displays, for example, are achieved by providing a host
liquid crystal material and mixing therewith dichroic dyes of
various colors in suitable proportions to obtain a material which
absorbs radiation in all or part of the spectral range of about
400-700 nm, wherein the dichroic dyes of various colors include a
dye having the general formula: ##STR18## wherein X, X', Y, Y', Z
and Z' are the same as defined above, and wherein at least one of X
and X' is a 5-membered ring connected to the benzene ring at the
lateral positions 2 and 3 and/or 6 and 7 of the lateral benzene
rings in the anthraquinone molecule, said 5-membered ring having
the structure ##STR19## wherein R is the same as defined above. The
suitable proportions of various dyes can be easily determined by
one skilled in the art. Examples of suitable proportions of various
dyes to form various colors are shown below where Examples 1, 3, 4
and 8 illustrate various dyes in designated proportions to produce
black colored compositions; Example 5 illustrates various dyes in
designated proportions to produce a blue colored composition;
Example 6 illustrates various dyes in designated proportions to
produce a violet colored composition; and Example 7 illustrates
various dyes in designated proportions to produce a green colored
composition.
The appropriate mixture of dichloric dyes of various colors in
suitable proportions to obtain a material which absorbs radiation
in the spectral range of about 400-700 nm, and which approaches a
substantially black appearance in color, is within the purview of
one skiilled in the art, and the improvement of the present
invention is directed to the use of one or more of the
anthraquinone-based dyes having the designated 5-membered,
N-substituted dicarboximide ring structure to improve the
"blackness" of the dichroic dye mixture in a liquid crystal display
made from various colors. The greenish color of green dyes and the
bluish color of blue dyes, and the like, are also improved from the
use of the anthraquinone-based dyes of the present invention in a
liquid crystal. When about 0.5% to about 1.0% or higher by weight
of the blue anthraquinone-based dyes of this invention are used
with about 0.5% to about 1.0% or higher by weight of other dichroic
dye or dyes, the colors of the liquid crystal displays are
substantially improved in a biphenyl liquid crystal, and depending
upon the relative amounts of dyes used, displays of various shades
and colors of green, blue and black are obtained including
greenish-black, blue-black, grey-black and greenish-blue, and there
is little or no reddish tint or color in such displays. The
anthraquinone-based dyes of this invention used in such mixtures
have substantially high order parameter (S), generally at least
above 0.60, to ensure satisfactory brightness and contrast ratio.
As indicated above, order parameters higher than 0.60 are not
frequently achieved in liquid crystal compositions when dyes having
maximum absorption peaks above 650 nm are dissolved therein.
Any liquid crystal host material may be used in accordance with the
present invention. In those embodiments of the present invention
wherein the anthraquinone-based dichroic dye material having at
least one 5-membered, N-substituted dicarboximide ring structure
thereon, is used as a guest dye in a host liquid crystal material,
it is not critical which of the many well known liquid crystal
materials or combinations thereof may be used as long as the
anthraquinone-based dye materials of the present invention are
soluble in the host liquid crystal material and as long as the
anthraquinone-based dye or dyes of the present invention are
compatible with or have no adverse effect upon the host liquid
crystal material. In preferred liquid crystal compositions of the
present invention, the host liquid crystal material is a nematic
liquid crystal of positive or negative dielectric anisotropy, a
cholesteric liquid crystal of positive or negative dielectric
anisotropy and mixtures thereof, that is, mixtures of nematic
liquid crystals and cholesteric liquid crystals modified with other
optically active compounds.
Any conventional liquid crystal host material can be used with the
anthraquinone-based dyes of the present invention. The liquid
crystal hosts can be selected by one skilled in the art depending
upon the electro-optic effect to be utilized. Nematic liquid
crystals include the biphenyl liquid crystals such as E7 and E8
from BDH, Ltd., phenylcyclohexanes and azoxy mixtures available
from E. Merck. Co., alkoxybenzylidene anils such as those having
the structural formula: ##STR20## wherein OR is an alkoxy radical
preferably having from 1 to 7 carbon atoms or an acyloxy radical
having from 2 to 7 carbon atoms, p-anisylidene-p'-n-butylaniline,
p-anisylidene-p'-aminophenylbutyrate,
p-(p'-methoxyphenylazoxy)butylbenzene, p-(p'-ethoxyphenylazo)
phenylheptanoate, p-n-hexylbenzoic acid-p'-n-hexyloxyphenyl ester,
and other liquid crystal materials, such as the esters disclosed in
U.S. Pat. No. 3,984,344, p-n-hexylbenzylidene-p'-aminobenzonitrile,
p-capryloxybenzylidene-p'-aminobenzoitrile,
p-cyanophenyl-p'-n-heptylbenzoate,
p-cyanobenzylidine-p'-n-butoxyaniline,
p-cyanobenzylidene-p'-amino-phenylvalerate, p-azoxyanisole,
butyl-p-(p'-ethoxyphenoxy-carbonyl)phenylcarbonate,
p(p'-ethoxyphenylazo)phenylheptanoate, and the like. Another class
of liquid crystal materials have the general formula: ##STR21##
wherein R is an alkyl or alkoxy group and m=0 or 1, at least one of
said compounds being cyanobiphenyl wherein m=0. Generally, nematic
liquid crystals fall within the class of chemical compounds having
the general formula: ##STR22## wherein X is an azomethine linkage
of the Schiff base class, X is an ester, vinylene, acetylene, azo
or azoxy, or X is merely a single bond connecting the two benzene
rings; and A and B are C.sub.n H.sub.2n+1 (alkyl group); C.sub.n
H.sub.2n+1 O (alkoxy group); or C.sub.n H.sub.2n+1 COO (ester
group). Cholesteric liquid crystals can be pure compounds such as
derivatives of cholesterol or noncholesteric materials. These are
characterized by optical activity arising from the absence of
molecular symmetry.
Examples of specific commercial nematic liquid crystals include E-7
from BDH Chemicals wherein the chemical structure is of the
biphenyl type, and the temperature range is -10.degree. to
60.degree. C. with a dielectric anisotropy of 11; E-8 from BDH
Chemicals having a basic chemical structure of the biphenyl type
with a temperature range of about -10.degree. to 70.degree. C. with
a dielectric anisotropy of 13; Licristal 1132 from E. Merck of the
phenylcyclohexane type having a temperature range of -6.degree. to
70.degree. C. with a dielectric anisotropy of 10; Licristal 1221
from E. Merck of the phenylcyclohexane type having a temperature
range of -10.degree. to 90.degree. C. with dielectric anisotropy of
8; ROTN-103 from Hoffman-LaRoche of the ester type having a
temperature range from about -10.degree. to 80.degree. C. with
dielectric anisotropy of 26; ROTN-200 from Hoffman-LaRoche of the
Schiff base type having a temperature range of about -15.degree. to
65.degree. C. with a dielectric anisotropy of 18; and ROTN-404 from
Hoffman-LaRoche of the biphenyl-pyrimidine type having a
temperature range from about -10.degree. to 105.degree. C. and a
dielectric anisotropy of 21.
The following examples further illustrate the practice of the
invention, and they are meant to be exemplary only and are not to
be construed as to limiting the invention in any way.
The following examples illustrate the use of the
anthraquinone-based dyes in two types of liquid crystal displays
having two different liquid crystal hosts. In one type of liquid
crystal display used to demonstrate the present invention, the
liquid crystal host was a cholesteric liquid crystal. In the other
type of liquid crystal display, the anthraquinone-based dyes were
dissolved in a nematic liquid crystal. In both cases, the resulting
cholesteric or nematic liquid crystal composition was sandwiched
between conductive glass plates in test cells whose surfaces are in
contact with the solution, the surfaces having been previously
rubbed unidirectionally. The test cells are conventional liquid
crystal cells having a distance of about eighteen microns between
the plates and a polarizer external to the cell. The boundary
condition inside the cell is homogeneous. When illuminated, the
display switches from a particular color, for example, green, blue,
or black, in the absence of an applied voltage to substantially
colorless in the presence of a voltage.
EXAMPLE 1
A black composition was prepared by mixing 2.85 grams of a
biphenyl-pyrimidine type liquid crystal having a temperature range
from about -10.degree. to 105.degree. C. identified as ROTN-404
from Hoffman-LaRoche Company, 0.15 gram of an optically active
chiral dopant identified as CB-15, 0.0025 gram of blue dye
4,4'-bis(4-N-ethylaminonaphthylazo)azobenzene, 0.01 gram of blue
dye
4,4'-bis[2,5-dimethyl-4-(4-ethylaminonaphthylazo)phenylzao]azobenzene,
0.025 gram of blue dye
4,4'-bis(4-ethylaminonaphthylazo)-2-methyl-5-methoxyazobenzene,
0.0025 gram of yellow dye
4,4'-bis(4-N,N-diethylaminobenzalamino)azobenzene, 0.0075 gram of
yellow dye 4,4'-bis(4-N,N-dimethylaminobenzalamino)azobenzene; and
0.0025 gram of an anthraquinone-based dye having a 5-membered,
N-substituted dicarboximide. CB-15 is 4-cyano-4'-(2-methyl)
butylbiphenyl having the formula: ##STR23## The anthraquinone-based
dye used in this example was
1,4-diamino-N-(3-methoxypropyl)-2,3-anthraquinone dicarboximide
having the formula: ##STR24## available commercially under the
trade name Genacron Brilliant Blue 8G and supplied by
BASF--Wyandotte.
The composition made with the dyes specified above was placed in a
conventional liquid crystal test cell as described above and having
a spacing between the plates of about 18 microns. In the absence of
voltage, the color of the display was neutral black. When a voltage
of about 15 volts was applied to the test cell, the neutral black
material turned substantially colorless.
The order parameter of
1,4-diamino-N-(3-methoxypropyl)-2,3-anthraquinone dicarboximide was
measured in liquid crystal E-7 described above and commercially
available from BDH Chemicals Company and was determined to be 0.66.
The order parameter of the same dye was 0.71 in ROTN-404 described
above and commercially available from Hoffman-LaRoche. The maximum
absorption peak was at 675 nm in both E-7 and ROTN-404.
EXAMPLE 2
A formulation was prepared as in Example 1 above without the
anthraquinone-based dye. When the composition was viewed in
incandescent light or daylight, the formulation had a reddish
hue.
EXAMPLE 3
A blue anthraquinone-based dye,
1,4-diamino-N-isopropyl-2,3-anthraquinone dicarboximide having the
formula: ##STR25## was made by the procedure described in Example 6
of U.S. Pat. No. 2,628,963.
A formulation identical to that disclosed in Example 1 above was
made with this blue dye in place of the
1,4-diamino-N-(3-methoxypropyl)-2,3-anthraquinone-dicarboximide dye
of Example 1. Substantially similar results were obtained when the
blue dye of this example replaced the dye of Example 1. There was
good dichroism in liquid crystal E-7 with the blue dye of this
example, however, it was also noted that there was low solubility
of the blue dye of this example in the liquid crystal formulation.
The order parameter of the dye of this example was estimated
between about 0.60 and 0.65 in liquid crystal mixture E-7 and in
liquid crystal mixture ROTN-404, and the absorption peaks were at
675 nm.
EXAMPLE 4
Another dye,
1,4-diamino-N-(.varies.-methylbenzyl)-2,3-anthraquinone
dicarboximide, having the formula: ##STR26## was made in accordance
with the procedure described in Example 3 using
.varies.-methylbenzyl alcohol instead of the isopropyl alcohol of
Example 3. This anthraquinone-based dye was substituted for the
anthraquinone-based dye in Example 1 above, and substantially the
same results were obtained using the dye of Example 4.
The order parameter of the blue dye of this invention was estimated
at between about 0.60 and 0.65, and the absorption peaks were at
about 675 nm. Although there was limited solubility of the dye of
this example in the liquid crystal formulation of Example 1, there
was a definite improvement in the color of the formulation when the
dye was used.
EXAMPLE 5
Blue liquid crystal compositions were prepared by mixing 2.85 grams
of ROTN-404, 0.15 gram CB-15, 0.015 gram of purple dye
4,4'-bis-(N,N-diethylamino-2-methylphenylazo)azobenzene and 0.0045
gram of the anthraquinone-based dye used in Example 1 above. The
formulation was placed in a conventional test cell, and in the
absence of a voltage, the color of the liquid crystal composition
was blue. When a voltage of about 15 volts was applied, the liquid
crystal composition turned substantially colorless. When the
anthraquinone-based dye was omitted from the formulation, the
display had a purple color which was less pleasing than the blue
color obtained with the blue dye.
Substantially similar results were obtained when the
anthraquinone-based dye of Example 1 was replaced with the
anthraquinone-based dye of Example 3, and when the
anthraquinone-based dye was replaced with the anthraquinone-based
dye of Example 4.
EXAMPLE 6
As in the preceeding examples, a cholesteric liquid crystal
composition having a violet color was prepared by mixing one gram
of ROTN-404, 0.05 gram of CB-15, 0.05 gram of orange-red dye
4-(4-dimethylaminophenylazo)azobenzene produced by BDH Chemicals
Company and 0.005 gram of the anthraquinone-based dye used in
Example 1 above. The violet-colored formulation became
substantially colorless when an electric field was applied to a
conventional test cell containing the formulation of this example.
When the anthraquinone-based dye was omitted, the color of the
formulation was orange-red when an electric field was applied to
the cell containing the composition.
Substantially similar results were obtained when the
anthraquinone-based dye of Example 3 replaced the
anthraquinone-based dye of Example 1, and when the
anthraquinone-based dye of Example 4 replaced the
anthraquinone-based dye of Example 1.
EXAMPLE 7
A cholesteric liquid crystal composition having a green color was
prepared by mixing 1.0 gram of ROTN-404 described above, 0.05 gram
of CB-15, 0.005 gram of yellow dye
4,4'-bis(4-N,N-dimethylaminobenzalamino)azobenzene and 0.005 gram
of the anthraquinone-based dye of Example 1. When a voltage of
about 15 volts was applied to the green formulation of this
example, the green formulation turned substantially colorless. When
the anthraquinone-based dye of this example was replaced with one
of the blue dyes in Example 1 above, such as blue dye
4-4'-bis(4-N-ethylaminonaphthylazo)azobenzene, the formulation gave
an unsatisfactory green color.
Substantially similar results were obtained when the
anthraquinone-based dye of Example 1 was replaced by the
anthraquinone-based dye of Example 3 in the formulation of this
example, and when the dye of Example 1 was replaced with the dye of
Example 4 in the formulation of this example.
EXAMPLE 8
This example demonstrates the use of the anthraquinone-based dyes
of this invention in a nematic liquid crystal host. A black liquid
crystal composition was prepared by mixing ten grams of
phenylcyclohexane nematic liquid crystal supplied commercially as
Licristal 1291 by E. Merck Company, 0.01 grams of blue dye
4,4'-bis(4-N-ethylaminonaphthylazo)azobenzene, 0.038 gram of blue
dye
4,4'-bis[2,5-dimethyl-4-(4-ethylaminonaphthylazo)phenylazo]azobenzene,
0.008 gram of yellow dye
4,4'-bis(4-N,N-diethylaminobenzalamino)azobenzene, 0.03 gram of
yellow dye 4,4'-bis(4-N,N-dimethylaminobenzalamino)azobenzene and
0.01 gram of the anthraquinone-based dye of Example 1. The
formulation was placed in a conventional test cell having a
distance of about 18 microns between the glass plates, the inner
surfaces of which had been rubbed unidirectionally to control the
alignment of the liquid crystal. A single polarizer was attached to
the cell. The resulting black display turned substantially
colorless when a voltage of about 15 volts was applied thereto.
When the anthraquinone-based dye was omitted from the formulation,
the black color of the formulation had a reddish tint when viewed
in daylight or incandescent light.
Substantially similar results were obtained when the
anthraquinone-based dye of Example 3 was used in place of the
anthraquinone-based dye of Example 1 in the formulation of this
example. Substantially similar results were obtained when the
anthraquinone-based dye of Example 4 was used in place of the
anthraquinone-based dye of Example 1 in this example.
EXAMPLE 9
Other blue dyes having a 5-membered, N-substituted dicarboximide
ring structure joined to the anthraquinone molecule in the 2 and 3
position and having the formula: ##STR27## were prepared for
testing and are shown in Table I below. The dyes were prepared in
accordance with the procedure described in U.S. Pat. No. 2,628,963.
R and the amine from which R is derived in the reaction mixture,
that is, the corresponding amine, are shown in Table 1 along with
the data collected and observed from each of the blue
anthraquinone-based dyes.
TABLE 1
__________________________________________________________________________
DYE CORRESPONDING OBSERVED NO. R AMINE DATA
__________________________________________________________________________
1 cyclohexyl cyclohexylamine S = 0.73 in Licristal 1291 S = 0.73 in
ROTN-404 2 CH.sub.2CH.sub.2C.sub.6 H.sub.5 1-phenyl-2-aminoethane 3
C.sub.8 H.sub.17 n-octylamine S = 0.64 in ROTN-404 S = 0.54 in E-7
##STR28## p-aminophenol S = 0.69 in Licristal 1291 5 C.sub.6
H.sub.13 n-hexylamine S = 0.66 in Licristal 1291 6 ##STR29##
p-aminophenylbenzoate S = 0.77 in ROTN-404 .lambda. max = 682 nm 7
C.sub.6 H.sub.5OC.sub.6 H.sub.13 p-hexyloxyaniline S = 0.74 in
Licristal 1291 .lambda. max = 684 nm
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In accordance with the present invention, black and colored
dichroic liquid crystal displays having improved absorption at the
600-700 nm range have been prepared and demonstrate superior color
balance in daylight and incandescent light over the prior art dyes.
Black liquid crystal displays, blue liquid crystal displays, green
liquid crystal displays, and other colors of liquid crystal
displays have been prepared with the anthraquinone-based dyes of
the present invention wherein a 5-membered, N-substituted
dicarboximide ring structure joins the anthraquinone molecule in
the lateral carbon atom positions of the lateral ring or rings of
the anthraquinone molecule to improve the color of the display.
Black and blue displays have been prepared without the customary
reddish hues. Green displays have been prepared with a more
pleasing green appearance. Violet-colored liquid crystal displays
have been prepared without the customary orange-red hues.
While other modifications of the invention and variations thereof
which may be employed within the scope of the invention, have not
been described, the invention is intended to include such
modifications as may be embraced within the following claims.
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